200 



SCIENCE 



[N. S. Vol. XXVI. No. 659 



chart of the island. I have visited the 

 site, and the foundations of the observatory 

 still remain. Halley's observations were 

 much hindered by cloud. On his return to 

 England, Halley in 1679 published his 

 "Catalogus Stellarum Australium," con- 

 taining- the magnitudes, latitudes and 

 longitudes of 341 stars, which, with the 

 exception of seven, all belonged to the 

 southern hemisphere. 



But the first permanently valuable as- 

 tronomical work in the southern hemis- 

 phere was done in 1751-52 by the Abbe de 

 Lacaille. He selected the Cape of Good 

 Hope as the scene of his labors, because it 

 was then perhaps the only spot in the 

 world situated in a considerable southern 

 latitude which an unprotected astronomer 

 could visit in safety, and where the neces- 

 sary aid of trained artisans to erect his 

 observatory could be obtained. Lacaille 

 received a cordial welcome at the hands of 

 the Dutch governor Tulbagh: he erected 

 his observatory in Cape Town, made a cata- 

 logue of nearly 10,000 stars, observed the 

 opposition of Mars, and measured a short 

 arc of meridian all in the course of a single 

 year. Through his labors the Cape of 

 Grood Hope became the birthplace of as- 

 tronomy and geodesy in the southern 

 hemisphere. 



Bradley Avas laying the foundations of 

 exact astronomy in the northern hemis- 

 phere at the time when Lacaille labored at 

 the Cape. But Bradley had superior in- 

 struments to those of Lacaille and much 

 longer time at his disposal. Bradley's 

 work is now the basis on which the fair 

 superstructure of modern astronomy of 

 precision rests. His labors were continued 

 by his successors at Greenwich and by a 

 long series of illustrious men like Piazzi, 

 Groombridge, Bessel, Struve and Arge- 

 iander. But in the southern hemisphere 



the history of astronomy is a blank for 

 seventy years from the days of Lacaille. 



We owe to the establishment of the 

 Royal Observatory at the Cape by an 

 Order in Council of 1820 the first success- 

 ful step towards the foundation of astron- 

 omy of high precision in the southern 

 hemisphere. 



Time does not permit me to trace in de- 

 tail the labors of astronomers in the south- 

 ern hemisphere down to the present day; 

 and this is the less necessary because in a 

 recent presidential address to the South 

 African Philosophical Society^ I have 

 given in great part that history in con- 

 siderable detail. But I have not there 

 made adequate reference to the labors of 

 Dr. Gould and Dr. Thome at Cordoba. To 

 their labors, combined with the work done 

 under Stone at the Cape, we owe the fact 

 that for the epoch 1875 the meridian side- 

 real astronomy of the southern hemisphere 

 is nearly as well provided for as that of 

 the northern. The point I wish to make is 

 that the facts of exact sidereal astronomy 

 in the southern hemisphere may be re- 

 garded as dating nearly a hundred years 

 behind those of the northern hemisphere. 



THE CONSTITUTION OF THE UNIVEESE 



It was not until 1718, when Edmund 

 Halley, afterwards Astronomer Royal of 

 England, read a paper before the Royal 

 Society,^ entitled " Considerations on the 

 Change of the Latitudes of Some of the 

 Principal Pixt Stars," that any definite 

 facts were known about the constitution of 

 the universe. In that paper Halley, who 

 had been investigating the precession of 

 the equinoxes, says: 



But while I Avas upon this enquiry I was sur- 

 prised to find the latitudes of three of the principal 

 stars in heaven directly to contradict the supposed 



' Trans. South African Phil. Soc, Vol. XIV., 

 part 2. 



» Phil. Trans., 1718, p. 738. 



